Like many patternshops, Sherwood Metal Products, Inc had an inauspicious beginning. In fact, Bill Wilson, Sr. started the company in his garage after working as a patternmaker for job shops and various GM divisions.

Twenty-four years later, the Drayton Plains, MI, company employs more than 50 people. Bill, Sr., now chairman of the board, maintains a consulting interest. His son, company president Bill Wilson, Jr., heads a fully integrated CAD/CAM patternshop.

Sherwood Metal Products' mainstay has always been automotive tooling and prototypes. For many years the company profited from a longstanding relationship with GM's nearby Pontiac Foundry. But it was Sherwood's expertise and reputation that led it to rebound after Pontiac closed several years ago. Bill Wilson, Jr. believes his company's commitment to CAD/CAM, beginning in the early '80s, was the key to success.

"We have made a commitment to CAD along with a commitment to accuracy and tolerances," he said. "In the past three years we have invested close to $2 million in new machinery and equipment that can give us the closer tolerances we find increasingly demanded of us."

Wilson believes Sherwood is one of only a few patternshops producing engine tooling completely from CAD/CAM. Evidence of the firm's CAD/CAM success is displayed at the company--a model of a V-6 engine, ten coreboxes, a cope and drag pattern that were machined out of solid blocks of magnesium.

Sherwood also has a big prototype business. Among the latest projects are new glass-reinforced nylon intake prototypes for a major auto manufacturer. The new manifolds, which are lighter and more heat resistant (up to 500F), may provide improved gas mileage and reduced emissions.

The first manifold model, made out of acrylic, is tested for flow. The final model is then sectioned, machined and all the interior parts duplicated before being laminated together. After the outside shape is duplicated, all the tape work is done for the holes, seals and steel liners.

Calling the Tune

Harold Anderson, director of CAD/CAM operations, sees parallels between what happened in tooling for auto body panels several years ago and what is now happening in the rest of the automotive tooling industry.

"The Big Three automakers were going into CAD 100% in the body panels, and the people who didn't have CAD weren't getting the work," he said. "What's done right now is that GM will supply the database--you don't get a drawing or anything else--and if you can't read or manipulate the database, you're out of business. I believe it is going to happen in the pattern industry. They are only going to give you a database and you're going to have to deal with it."

Ironically, a few patternshops like Sherwood have something the automakers don't have: the whole job captured in a computer along with all of the surfaces and geometry it takes to build the job.

"It's their part and they don't have that," Anderson said. "If we had the time or wanted to invest the money, we could actually take that part and turn it into a database, and actually supply the database."

Jim Pope, vice president, added: "They had the systems before we did, but with a large company, it really takes them a lot longer to fully utilize the 'tool.' We're able to use it right now. I see the automakers relying more on the patternshops. Some of the jobs we have received have been lacking in information, and we've had to step in and help them out quite a bit more just in product design."

Pope and the rest of the Sherwood staff believe that design engineers will have to become more acclimated to the pattern part itself, designing the part in 3-D.

The increased use of CAD also may mark the return of casting drawings. Casting drawings show where the parting lines are, from where the drafts are generated and all the finished stock. The split line may be made differently at various shops. While frequent design changes are expensive to document on hand-drawn prints, computer plotters can render a complex CAD print in minutes.

Determining where the parting lines will go is left up to the patternmaker. In this regard, Anderson believes foundry patternshop experience is invaluable to would-be CAD operators.

"CAD/CAM graduates don't have the practical knowledge of how the part will be built," he said. "We are always dealing with partings, drafts running in opposite directions and metal walls. Even the engineer who designed the original part doesn't always know what he or she will end up with. They give you their concept and then you have to make it work."

CAD/CAM has evolved to the point where the entire surface can be machined. Says Anderson: "In its infancy, those using CAD/CAM did the easy stuff. Where a compound-angle surface came into another angled surface, they just stopped--they couldn't do the fillet between the two surfaces. Even today, a lot of the systems don't handle the fillets real well. But today we can create the surface and program the cutter ball to the precise position required to create the fillet."

Tightening Tolerances

Another major concern which has pushed patternshops to adopt CAD/CAM technology is the increasingly tighter tolerances demanded by the automakers.

According to Pope, a pattern designer for 12 years, the situation is changing rapidly.

"Within the past year, when a job was let out for bids, one of the major automakers started specifying that the models must be 100% CAD or 100% NC, where as before it was left up to the discretion of the patternshop," Pope said. "The shops are starting to get into it, and there are enough of them into it now that automakers can demand it.

"The major automotive companies want [+ or -] 0.003 in. everywhere--on models, core prints and partings. They want critical casting areas held to [+ or -] 0.003, and in some cases [+ or -] 0.001. The last two quotes, from major foundries, were requested as 100% CAD, [+ or -] 0.003 overall, including shape. Up until just the last year this was unheard of. You have to have an almost perfect model to get these tolerances.

"There are certain jobs, like single patterns, where you might have six or a dozen, but they are in one piece. You can actually NC the shape; you don't have to duplicate it.

"But take, for instance, a corebox with six cavities. If you used NC for the entire shape, it could take you six times as long compared to duplicating all six cavities at the same time because you can only machine the one cavity at a time versus doing six of them at a time. Our CAD/CAM-produced model is dimensionally accurate enough that we can use the electronic duplicator to produce world-class tooling."

In some cases CAD/CAM permits bypassing the model altogether. Sherwood was asked to change the shrink on an existing bearing cap model. After digitizing the part, a profile and contour controlled milling machine was used to make the new model, saving $4000-$5000 over traditional methods.

Reaching Out

Although Sherwood farms out much of the casting machining and all of the coordinate measuring, both operations may be brought in-house. Part of the impetus for such a move would be increased control over scheduling, part the added profit, but also the opportunity to pick up more outside business.

"All of our other nonpattern related business that we do right now with patternmakers we could do more economically with nonpattern technicians," Pope said. "Just like those nylon parts, those are not patterns but parts. We just don't have a significant amount of that work right now--maybe $300,000-$400,000 per year--that we could hire people to do just that. But I think it is coming.

"Right now we might get a run of 100 prototype parts. We machine anything from a small cam cover to a complete block. Whether or not there's a market for machining at this point needs to be explored. More and more, the Big Three are going outside--just buying the finished casting.

"We are trying to broaden our customer base. We lost a big customer when they closed Pontiac--they were probably 75% of our business. But we've managed to get enough business to do well."

Ross Biondo, treasurer and manager of shop operations, sees GM's Targets for Excellence program as more than an opportunity for Sherwood to keep GM as a customer.

"In the past three months we've spent a lot of time and money redoing surface plates, checking and certifying," he said. "We hope that what we learn will help us in possible future audits by other automakers."

However, there is another side to the audit process.

"It's not just a matter of passing the audit," Wilson said. "We see a number of pluses from the audit process that can be quite beneficial to our system. We didn't document maybe as well as we should have. It's been a good system and worked for us for years and we've always produced quality tooling. But as far as tracking, there's a lot of good that came of it for us that may help us align and maybe determine goals a little better than we have in the past.

"You look at it and think, 'This is a lot of work and why are they doing this to us?' But as we get into it, we're finding that we're learning more and more how we can use it to help us."

GM also may be reassessing and tailoring the audit program to specific types of suppliers.

"I think they are realigning it because Targets for Excellence was originally intended for large parts suppliers," Wilson said. "We're more of a service industry to them. They are in the process of coming up with a few new guidelines that would be more specific to our area."

COPYRIGHT 1990 American Foundry Society, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.